No, in general they aren't interchangeable, and here a good site and some good example phrases:

http://www.learn-spanish-online.de/grammar/chapter12_prepositions/12_14_a_traves_de.htm
http://www.learn-spanish-online.de/grammar/chapter12_prepositions/12_3_por.htm#sechs

Thanks for researching that for me Pablo but I still don't understand.

Hay veces que 'through? pueda significar 'por? o 'a través de'. Es decir, cuando 'through? significa 'by means of? pueden ser intercambiables.

Ejemplos:

I listen to the news through the televisión. (Escucho las noticias a través de/por la televisión).
I heard about the accident through my sister. (Me enteré del accidente a través de/por mi hermana).

Hay otra expresión en la que es intercambiable: when you see something through the window (cuando ves algo a través de/por la ventana).

Luego, 'through? se utiliza para indicar 'de parte a parte? con idea de movimiento.

I walked through the park (yo paseaba a través del parque).

"Por" no siempre significa "through". Ejemplo: Paseo por/en el parque. En este caso "por" significa "in" porque no es "a través de".

Espero haberte podido ayudar.

So basically the only difference is that por means "in" in some cases'

So basically the only difference is that por means "in" in some cases?

Or "by" or "around/in the area of" and a number of other possibilities, depending on the context.

There has to be a more significant difference. Could someone give me an example were you can't put por in the place of a través de.

Luego, 'through? se utiliza para indicar 'de parte a parte? con idea de movimiento.

I walked through the park (yo paseaba a través del parque).

"Por" no siempre significa "through". Ejemplo: Paseo por/en el parque. En este caso "por" significa "in" porque no es "a través de".

Translation:

So "through" is used to indicate "from place to place" in respect to movement.

I walked through the park (yo paseaba a través del parque).

"Por" does not always mean "through." Example: Paseo por/en el parque. (I walk around/in the park.) In this case "por" means "in," because it is not "a través de" (across/through/from one extreme to the other).